This study looks at how well a medicine called Dexmedetomidine (DEX) helps children stay still during an MRI scan. An MRI is a special kind of picture that helps doctors see inside the body. Sometimes, it can be hard for kids, especially those under 5 or with autism, because they have to lie very still in a noisy tunnel for 20 minutes. Doctors usually use a strong medicine called Propofol that requires a breathing tube, but DEX is an easier option that can be given through the nose. This study will see if DEX works better in kids with autism or other brain-related conditions compared to other kids. Children under 18 years who received DEX for an MRI can participate, but not if their medical records are incomplete.

• The study is a retrospective review, so no new treatment will be given.
• It focuses on understanding DEX use for MRIs in kids with different conditions.
• Participants will not need to visit the study center as it uses past medical records.